High-definition (HD) resolution video content has become the trend for emerging streaming video systems. In regard to the large computation demand, distributed video coding architecture is considered as a cost-effective solution for coding, i.e., compressing live, HD video with low processing latency. See for example, U.S. patent application Ser. No. 11/539,514 to inventors Mauchly et al., titled VIDEO ENCODER WITH MULTIPLE PROCESSORS, that describes a coding apparatus that uses multiple coders which operate in different rows of the same slice of the same video frame. Data dependencies between frames, rows, and blocks are resolved through the use of a data network. Block information is passed between coders of adjacent rows. The apparatus can achieve low latency compared to other parallel approaches.
In many streaming video systems such as a video conferencing system, real-time detection of human faces in the video sequence is desired to improve the application quality. With detected face regions, for example, the video coder can assign smaller, that is, finer quantization step sizes to frame blocks that are within a face region while higher, i.e., coarser quantization step sizes are assigned to the remaining portion of the frame, which is expected to provide higher visual quality of the scene under the same bit rate.
Methods for face detection are known that require knowledge of the entire picture at the time of processing. In a distributed coding architecture wherein different parts of a picture may be processed simultaneously in different distributed elements, the entire picture may no longer be available.